The management of human malignant gliomas is made difficult by the extreme variability in the degree of differentiation existing within one tumor, as well as from tumor to tumor. The presence of heterogeneous population of cells with different biological characteristics is well proven in the past few years. Specific differentiation markers are available to study the process of malignant transformation. However, the relationship between differentiation, heterogeneity and the natural history of malignant gliomas is not well established. We propose to establish permanent and clonal cell lines from biopsy specimens obtained from different locations of untreated malignant gliomas during the initial operation and during subsequent re-operation for recurrent tumor, and to characterize chemosensitivity and tumorigenicity so as to assess the regional heterogeneity in biological behaviors, and to correlate in vitro chemosensitivity with in vivo response to chemotherapy. The expression of differentiation markers like glial fibrillary acidic protein (GFAP), and vimentin will be determined in the tissue specimens and the cell lines derived from these specimens in an attempt to correlate the expression of these markers with other biological characteristics, especially chemosensitivity, tumorigenicity and overall clinical course of the patient harboring the tumor, and to determine if dedifferentiation occurs as a glioma expands in size and recurs after treatment. We will study the evolution of GFAP and vimentin in vivo and in vitro by immunofluorescence and gel electrophoresis to determine the possible relationship between GFAP and vimentin. We also will perform cocultivation experiments to study cell-cell interactions between glioma cells and normal glial and endothelial cells. We hope that understanding in the process of differentiation/dedifferentiation in human gliomas and its relationship to cellular chemosensitivity and tumorigenicity may help us in designing better treatment programs, combining different treatment modalities, different chemotherapeutic agents and rational timing for the treatment of human gliomas.